WO2011135045A1

WO2011135045A1 - Planar luminous element having homogeneous light distribution and method for increasing the homogeneity of the light distribution of a planar luminous element

Info

Publication number: WO2011135045A1
Application number: PCT/EP2011/056777
Authority: WO
Inventors: Christian Kirchhof; Jörg AMELDUNG
Original assignee: Ledon Oled Lighting Gmbh & Co. Kg
Priority date: 2010-04-30
Filing date: 2011-04-28
Publication date: 2011-11-03
Also published as: EP2564442B1; CN102859742A; EP2564442A1; DE102010029848A1

Abstract

The invention relates to a planar luminous element, comprising a layer assembly (10) having a first electrode layer (11a), a second electrode layer (11c) and at least one light-emitting layer (11b) interposed between said layers, wherein a plurality of contact regions (12) for contacting the first electrode layer (11a) and at least one contact region (13) for contacting the second electrode layer (11c) are provided, wherein at least one contact region (12, 13) of the contact regions (12, 13) provided for contacting comprises a trimmable resistor (12a, 13a; 21a, 22a), or wherein a trimmable resistor (40) is connected between a contact region (12) provided for contacting the first electrode layer and a contact region (13) provided for contacting the second electrode layer, and wherein the resistance value of the trimmable resistor (12a, 13a; 21a, 22a; 40) can be set to a modified resistance value at which the light distribution of the layer assembly (10) is more homogeneous as compared to a state without a modified resistance value.

Description

Flat luminous element with homogeneous luminance and method for increasing the homogeneity of the luminance of a flat luminous element

description

The present invention relates to a flat luminous body with homogeneous luminance and a method for increasing the homogeneity of the luminance distribution over the emission surface of a flat luminous body, such as, for example, an OLED panel or OLED module.

On the basis of organic light emitting diodes (OLED = Organic Light Emitting Diode) novel lighting elements can be realized. As flat luminous bodies, which have a moderate luminance compared to inorganic LEDs (LED = light emitting diode), OLEDs are ideally suited for the production of flat, diffuse light sources, such as light panels. Large-area, diffused light sources are particularly desirable for general lighting applications, with which OLEDs have promising future potential for these applications. As a result of the thin-film technology used in the production of OLEDs, it may also be possible to realize flexible luminous bodies, which open up hitherto unknown possibilities for illuminating rooms.

For practical applications, in particular in general lighting, uniformly luminous OLEDs, ie OLEDs which emit light uniformly over their emission surface, are desired or required. Analogous to inorganic LEDs, organic LEDs are current-driven components. This means that the luminance of the OLED is correlated with the current flowing through the light-emitting, active layer of the OLED. For the realization of uniformly luminous OLEDs, therefore, a homogeneous current density over the areal extent of the OLED is required within the light-emitting layer. In the production of large-area light-emitting elements, however, this is a particular challenge. Typically, an OLED has at least one transparent electrode, which is realized, for example, by means of a transparent conductive oxide (TCO) or by means of transparent metal layers. However, since the electrical conductivity of these transparent electrode materials is low, the voltage drop within an electrode is not negligible. Due to the current-voltage characteristic of an OLED, small differences in voltage within an electrode surface have the effect of perceived, undesired brightness differences. If the luminance is required to be homogenous, the maximum Reachable luminous area size limited.

Due to the low electrical conductivity of the transparent electrode, it is often necessary to divide larger light areas into segments or individual areas. For a larger luminous area, a plurality of individual luminous elements are therefore to be combined, in which case an electrical contacting system is required in order to enable efficient control of large-area OLED luminous surfaces. This contacting system should be designed so that a maximum of homogeneous luminous surface can be achieved.

The standard structure of a conventional OLED can be summarized as follows. Essentially, an OLED or an OLED panel consists of two planar electrodes (at least one of which is transparent), between which at least one layer of organic materials is embedded. When applying a suitable voltage or impressing a suitable current, electromagnetic radiation, preferably light, can be emitted in the active organic layer. The OLED panel can be designed as a so-called bottom or top-emitting component. A transparent embodiment of the OLED is also possible. In a concrete example, indium tin oxide (ITO = Indium Tin Oxide) with a layer thickness of about 100 nm can be used as a transparent electrode, wherein the ITO layer is often applied to a glass substrate and can serve as an anode. This is followed by an organic layer or an organic layer structure, which may in some cases have up to 7 sublaid layers or layers, with a layer thickness of about 100 to 200 nm. Finally, a metallic cathode, which may comprise, for example, aluminum, with a layer thickness of approx. 100 to 500 nm thickness applied. As the size of the OLED panel increases, it becomes more difficult to achieve homogeneous light emission. The relatively high-impedance resistance of the ITO layer often leads to inhomogeneity of the luminance distribution in the case of large-area light-emitting elements. For example, the high-resistance resistor of the ITO layer may have a value of approximately 10 to 20 ohms / square (square). One reason for the inhomogeneity is, for example, that the contacting of the ITO layer for the power supply is often possible only in the peripheral regions of the luminous element. With a brightness of 1000 cd / m2 and a current efficiency of 50 cd / A, a typical OLED with a base area of 50 mm x 50 mm requires a current flow in the order of about 0.05 A during operation OLED contacted only from one side, this can lead to a voltage drop of the order of up to 0.5V. For conventional OLEDs, this voltage difference between the area of the connection to the Electrode and remote from the terminal portions of the electrode already a brightness difference, which is perceptible to the naked eye. At the operating point of an OLED, the current-voltage characteristic (IV curve) of an OLED is typically particularly steep, which is why small voltage differences within an electrode surface affect the luminance distribution. For example, for OLED panels characterized by a particularly steep IV curve, such a voltage difference can already account for a factor of more than 100 in the brightness of the component. In order to reduce the sheet resistance of the transparent electrode and thus to be able to achieve larger dimensions of the OLED panel, it is known to introduce metal reinforcements in the form of nets into the ITO layer. These metal grids (metal grids or so-called busbars) reduce the effective sheet resistance according to their occupation density and thus enable a realization of larger diode areas. However, the production of such a metal grid is technically complicated and requires several additional lithography steps in the manufacturing process. Due to the non-transparency of these metal grids also reduces the effective luminous area accordingly. For this reason, metal grids, for example, make sense only up to 25% of the ITO surface. A possible improvement would be, for example, an increase in the grid metal thickness, which, however, does not make sense due to structuring possibilities and the layer thicknesses of the organic layers. In addition, a metal-reinforced ITO layer is only contacted at the outer edges, whereby the maximum size of the luminous element remains limited despite the effective reduction in resistance. From WO09135466 it is known to compensate for the voltage drop across the electrode surface by an opposing resistance gradient within the organic layer (s). This resistance gradient can be achieved for example by irradiation, but this is technically complex to implement. Manufacturing tolerances, which occur due to process fluctuations in later manufacturing steps, can not be compensated in this case.

In addition to a low effective surface resistance of the transparent electrode, a uniform current feed is necessary for a uniformly radiating OLED. In order now to improve the homogeneity of the luminance distribution of the radiated light over the areal extent of the OLED, a plurality of feed points for the operating current are often provided on the OLED panel, ie there are several points at one or both electrodes, via which the electrodes are contacted. Typically, as symmetrical contacting of the OLED panel as possible is achieved. sought. In most cases, the anode has several contacting points, since these generally have a lower conductivity. But it can also be provided that the cathode or both electrodes, anode and cathode, have a plurality of contacting points, via which the operating current flows to or from. From DE 102006016373 Al an alternative approach for improving the homogeneity of the luminance distribution is known, in which a contacting region is formed as a peripheral frame in order to achieve a uniform feed of the operating current in the active OLED region.

Due to their complex structure, OLEDs are subject to certain process fluctuations and manufacturing tolerances during production. For example, inhomogeneities of the resistance within the electrode surface or even within the organic, light-emitting layer (s) can occur due to process fluctuations in the production. Likewise, it can lead to unevenness in the contacting, which can not be considered from the outset and compensated in the manufacturing process. Due to the current-voltage characteristics of OLEDs, even small manufacturing tolerances can adversely affect the homogeneity of the luminance.

The object of the present invention is therefore to provide a flat luminous element, which is characterized by the most homogeneous possible luminance and to provide a method for increasing the homogeneity of the luminance of a flat luminous element. The improvement in the homogeneity of the luminance should be feasible in a simple manner and as inexpensively as possible.

This object is achieved by a flat luminous element according to claim 1 and a method according to claim 10. Advantageous developments are the subject of the dependent claims.

The invention proposes a planar luminous body, in particular an OLED panel, which has a layer arrangement with a first and a second electrode layer and at least one light-emitting layer therebetween, wherein a plurality of contact areas for contacting the first electrode layer and at least one contact area for Contacting the second electrode layer are provided. Furthermore, at least to a contact region of the contact areas provided for contacting, a tunable resistance element is electrically connected in series, wherein the resistance value of the tunable resistance element is adjustable. If, therefore, the planar luminous body is contacted via this contact region, the current flow through this contact region is determined by the resistance value of the resistive element. The resistance value can preferably be changed to one Resistance value to be adjustable, in which the layer arrangement compared to a state without a changed resistance value has a more homogeneous luminance.

Optionally or alternatively to the abovementioned arrangement of the tunable resistance element according to the invention, in a preferred embodiment a tunable resistance element can be connected between a contact area provided for contacting the first electrode layer and a contact area provided for contacting the second electrode layer. This resistance element, which is comparatively high-impedance, is thus arranged electrically parallel to the light-emitting layer of the planar luminous element.

Differences in the connection resistances, caused by different transition and / or contact resistances at the individual contacting regions, can now be compensated for by means of the tunable resistor element. To a lesser extent, inhomogeneities of the resistance within the light-emitting layer (s) or within the electrode surface can also be compensated, primarily by the parallel arrangement of the tunable resistance element. Due to the parallel arrangement of the tunable resistance element, it is also possible to slightly modify the current-voltage characteristic of the flat luminous body.

According to the invention, by means of a corresponding adjustment process on the at least one tunable resistance element, a luminance which is homogeneous over the emission surface or at least one that is more homogeneous than an initial state without a resistance compensation is achieved.

The resistance of the tunable resistive element may be adjustable, for example, by means of a load trimming operation or a laser ablation process.

In a preferred embodiment, a planar luminous body, in particular an OLED module, is proposed, wherein the layer arrangement, which comprises the electrodes and light-emitting layer, is connected to a base element, for example a circuit board. The base member has interfacial areas on one of the first major surface facing the layer assembly, which are connected to the contact areas of the layer assembly, and external contacts on a second major surface, which are electrically connected to the associated intermediate contact areas on the first main surface of the board. According to the invention, the tunable resistance element can be connected in series between the intermediate contact region on the first main surface of the base element and the at least one contact region provided for contacting the layer arrangement is electrically connected, and be connected to the associated outdoor area. In addition, alternatively, a non-adjustable resistance element with a previously determined, required for a homogeneous luminance resistance serially between the intermediate contact region on the first main surface of the base element, which is connected to the at least one provided for contacting contact region of the layer assembly, and the associated external contact be switched.

According to the invention, the tunable resistance element may comprise a trimmable thick film resistor structure, a trimmable thin film resistor structure, a trimmable SMD resistor element or a trimmable integrated resistor structure. Furthermore, the tunable resistance element may include an adjustable potentiometer or a programmable electronic load circuit.

In an advantageous embodiment, the layer arrangement of the planar luminous body may have a plurality of contact regions for contacting the second electrode layer.

Furthermore, it can be provided that each of the contact areas provided for contacting has a tunable resistance element.

Preferably, the flat luminous element according to the invention is constructed of organic light emitting diodes, but the invention is not limited thereto. The invention can be applied to any two-dimensional luminous body in which a light-emitting layer is located between two planar electrodes, such as, for example, in a light-emitting electrochemical cell (LEC).

In the context of organic light-emitting diodes, the idea of the invention is applicable both to the contacting of an OLED panel and to an OLED module. In the context of the present invention, an OLED panel is understood as meaning a layer arrangement in which the individual layers (the two electrodes with the light-emitting layer structure therebetween) are applied to a substrate (for example glass). The entire arrangement may also be provided with an encapsulation for protection against the ambient atmosphere, ie against oxygen and humidity. The OLED panel can be designed as a bottom-emitting or top-emitting component. An OLED module is an arrangement in which an OLED panel is connected to a circuit board. The board can have defined electrical interfaces (external contacts), via which the OLED panel is supplied with operating current. The OLED module can be fastened to a carrier plate of a luminaire or can be detachably connected to a socket. be set, ie be installed in a simple manner without individual adjustment in a lamp. Among other things, the board has the function of distributing the current from one or more defined interfaces, which if possible are standardized, to the respective contact areas optimized to the individual shape of the OLED panel. Optionally, additional electronics with additional functions can be provided on the board.

The invention further includes a method for increasing the homogeneity of the luminance of a planar filament. In order to reduce inhomogeneities in the luminance of the flat luminous element, an adjustment of one or more resistance elements is made according to the invention to the contact areas provided for contacting the planar luminous element. In this way, a more uniform contacting of the luminous element and thus a more homogeneous luminance distribution over the surface of the luminous element compared to an (inhomogeneous) initial state can be obtained without performing a calibration on one or more resistance elements.

In order to determine the required resistance values on the tunable resistance elements for the desired homogeneous luminance distribution of the luminous element, suitable parameters or characteristics are required which allow conclusions to be drawn about luminance inhomogeneities. According to the invention, a homogeneity measurement of the luminance of the luminous element can be carried out, in which a position, extent and / or luminance of one or more inhomogeneities in the luminance distribution over the emission surface of the luminous element are detected as exemplary measurement parameters. Alternatively, differences in the contact or contact resistances or asymmetries of the electrode layer resistances can be determined metrologically by impressing a measuring current alternately between respectively different contacting pairs, wherein a contacting pair is formed by two different contacting regions. Conductivity measurements can then be used to determine possible asymmetries at the contact areas provided for contacting the filament.

Based on parameters detected in this way, it is now possible to conclude an asymmetrical feeding of the operating current or an inhomogeneity of the operating current distribution in the active region of the luminous element and thus the respectively required resistance value or the required change of the resistance value at the tunable resistance element. Based on the determined resistance value for the at least one contact region then the adjustment of the resistance value is performed on the tunable resistance element. According to the invention can equally the respective required resistance value for several or all contact areas (ie for the divided anode and / or cathode) are determined and then the adjustment of the resistance values are performed on these adjustable resistance elements. The resistance equalization can be carried out, for example, by means of a laser trimming process or a laser ablation process.

Further, for setting the determined resistance value, it is also possible to insert a respectively suitable series resistance element on at least one of the contact areas of the planar luminous element provided for contacting, the resistance value of the resistance element to be used having the resistance value provided for a more homogeneous luminance density distribution. Here, too, the respectively suitable series resistance element can be determined and set for one, several or all contact areas.

The determination according to the invention of the resistance value required for a (possibly) homogeneous luminance distribution of the luminous element can be carried out in each case for one, several or all contact regions of the luminous element. Accordingly, the adjustment to the desired resistance values can be carried out at one, several or all contact areas. Thus, a resistance value for a homogeneous luminance distribution of the luminous element can be determined for each contact area with a tunable resistance element, and the respective particular resistance value can be set. Preferably, the adjustment of the tunable resistance elements can be carried out individually at the different contact areas, so that after adjustment at the contact areas substantially the same resistance to the luminous body is present, which enables a more homogeneous luminance distribution of the filament. Alternatively, the adjustable resistance elements can be increased uniformly to respectively increased resistance values, so that due to the increased series resistance possible interfering, different contact and contact resistances at the contact areas do not or significantly less affect the luminance density distribution.

It should also be noted in the context of the present invention that the reference to the resistance value or the resistance values which are required for a homogenous luminance distribution of the luminous element does not necessarily correspond to the absolutely exact resistance values for an absolutely exact homogenous luminance distribution or symmetrical contacting but, for example, within a tole- Ranges of 50%, 20%, 10%> or 1% indicate the required resistance values, which contribute to an increase (or to achieve) the homogeneity of the luminance distribution over the emission surface of a flat light body. Thus, according to the invention, first of all a resistance value is determined on at least one of the plurality of contact areas of the luminous element provided for contacting, which resistance is required (within a tolerance range) for a homogenous luminance distribution of the luminous element.

Based on this determined resistance value, the resistance value at this contact region (within a tolerance range) is then set to the resistance value required for a more homogeneous luminance distribution of the luminous element.

The aim of the invention is thus to achieve the highest possible homogeneity of the luminance over the emission surface of the planar filament.

The invention will be explained in more detail with reference to the accompanying drawings. 1 a-b show a schematic plan view of an OLED panel and a detailed view of contact areas of the OLED panel according to an exemplary embodiment of the present invention;

2a-b is a schematic plan view of an OLED panel and a detailed view of contact areas of the OLED panel according to another embodiment of the present invention;

3 shows a schematic plan view of an OLED panel with contact areas according to a further exemplary embodiment of the present invention; and

4a-b is a schematic side view of an OLED module and a schematic plan view of a portion of the OLED module according to another embodiment of the present invention.

Before the present invention is explained in more detail in detail below with reference to the drawings, it is pointed out that functionally identical or equivalent elements in the figures are provided with the same reference numerals, so that Description of these elements shown in different embodiments is interchangeable or can be applied to each other.

FIG. 1a now shows a plan view of an OLED panel 10. An example of an OLED panel was mentioned in the introduction. The OLED panel 10, which may, for example, be in the form of an OLED plate or OLED film, has a layer stack 11 which is applied to a substrate. The OLED panel may be rigid (as an OLED plate), for example when a glass plate is used as a substrate. The OLED panel may also be flexible (as an OLED film), if, for example, a film is used as the substrate. As substrate materials, metal foils are also conceivable, for example, in which an insulating layer is applied before the active layer stack 11 is formed. The active layer stack 11 has a first electrode layer 11a (eg an anode layer), a second electrode layer 11c (eg a cathode layer) and at least one organic light-emitting intermediate layer 1bb, which is between the first electrode layer 11a and the second electrode layer 11c is arranged on. Furthermore, contact regions 12, 13 are arranged on the surface of the OLED panel 10 for contacting the active layer stack 11.

In the figures la-b, the OLED panel 10 has a square basic shape, which is to be assumed as purely exemplary. It is conceivable to use OLED panels of any geometry as the basic form, whereby the basic shape (the shape of the substrate) also depends on the shape of the active layer stack 11, i. the actively lit field, can distinguish.

In the exemplary embodiment illustrated in FIGS. 1a-b, the OLED panel 10 has, for example, a plurality of contact areas 12 for contacting the first electrode layer 11a and at least one contact area 13 for contacting the second electrode layer 11b. The contact areas 12 form, for example, the anode contact areas which make contact with the anode layer for supplying an operating current, while the contact areas 13 are formed, for example, as cathode contact areas which contact the cathode layer for decoupling the operating current. Alternatively, the first electrode layer 1 la may be formed as a cathode layer and the second electrode layer 1 lc as an anode layer, so that then the contact region 12 is formed as a cathode contact region and the contact region 13 as an anode contact region.

In the example shown here, the layer arrangement 10 has two contact areas 12 (eg anode contact areas) for contacting the first electrode layer 11a and a contact area 13 for contacting the second electrode layer 11c (eg Cathode contact area). Alternatively, the layer arrangement 10 could also have two contact regions 12 formed as cathode contact regions and a contact region 13 formed as an anode contact region. In a preferred embodiment, the contact regions 12, 13 are arranged in the region of the corners.

The exact number, positioning and shape of the contact areas 12, 13 are of minor importance to the invention. Preferably, the contact regions 12, 13 are arranged so that the most uniform possible current distribution in the OLED panel and an associated uniform current distribution within the active layer 11 of the OLED panel 10 is possible. It should be noted that in addition to the contact areas 12, 13 shown in FIG. 1a, additional or differently positioned contact areas 12, 13 may be provided. A preferred variant has contact regions 12, 13 in the region of all four corners (the additional contact regions are marked with optional in FIG. 1a). The respective contact regions 12, 13 may be formed as elongated strips or in another geometric shape along the edge region of the OLED panel 10. Thus, the contact regions 12, 13 may be arranged in pairs on several or all edge or corner regions of the OLED panel.

Due to manufacturing tolerances or process fluctuations, it is now impossible to predict contact and contact resistances between the respective contact regions 12, 13 and the electrodes of the layer stack 11, wherein even small asymmetries in the connection resistors or electrode resistors can lead to luminance homogeneity on the OLED panel 10 , According to the invention, tunable resistive elements 12a are provided in the region of the contact regions 12, 13, via which current flows when contacting.

In order to counteract the incidence of inhomogeneity of the luminance of the OLED panel 10 due to uneven contacting of the OLED panel 10, the contact areas 12, 13 of the OLED panel 10, which are initially provided on at least one of the plurality of contact areas, will now be the one for a more homogeneous luminance distribution the OLED panel 10 required resistance value, in which, compared to an unchanged resistance value, a more homogeneous luminance distribution of the layer arrangement 10 results. For this purpose, for example, the homogeneity of the luminance distribution achieved by the OLED panel 10 is evaluated in the case of an operating current feed, wherein, for example, a position, extent and / or luminance of an inhomogeneity in the luminance distribution relative to the emission surface of the planar luminous body 10 is detected as the measurement parameter. Based on this detected parameter in the form of position, extent and / or luminance of an inhomogeneity can now for a more homogeneous luminance distribution required resistance value at one or more of the contact areas provided for contacting 12 can be determined.

If it should now be established that one of the contact regions provided for contacting the first electrode layer I Ia has an increased contact or contact resistance compared to the second contact region provided for contacting the first electrode layer I Ia, the resistance value of the contact region with the lower resistance value can now be determined be increased by means of a resistance compensation in order to obtain a more homogeneous luminance distribution of the layer structure.

According to embodiments of the present invention, it is alternatively possible, even with both provided for contacting the first electrode layer I Ia contact areas 12, 13 to set their resistance value by means of a resistance adjustment so that at both contact areas 12 a (within a tolerance range) is the same contact resistance , Furthermore, it is possible to increase the resistance value at both contact regions 12 provided for contacting the first electrode layer 11a so that possible contact and contact resistances have little or no negative influence on a homogeneous luminance distribution or on a symmetrical feed of the operating current. In the case of these two latter alternatives, a series resistor or series resistor, which is arranged in series with the operating current feed into the OLED panel, is thus provided by the resistance compensation of the two contact regions 12 provided for contacting the first electrode layer 11a.

In order to provide a calibratable resistance element 12a at a contact region 12, the respective contact regions 12 provided for contacting the first electrode layer 11a can be configured as tunable or trimmable thick-film resistor structures or thin-film resistor structures or, for example, a trimmable SMD resistor component or a trimmable integrated Resistor structure, wherein the adjustment process can then be performed by means of a laser trimming operation or a laser ablation process. Alternatively, any suitable process for the targeted removal of material of the resistive element for adjusting the resistance value can be used.

1b shows an enlarged detail view of a corner region of the OLED panel 10 and the contact regions 12, 13. FIG. 1b shows by way of example a contact region 12 for contacting the first electrode layer 11a, which has, for example, a tunable resistance element 12a non-adjustable contact area 13 for contacting the second electrode layer 11c shown. The resistance value of the Contact area 12 for contacting the first electrode layer I Ia be changed by laser trimming or laser ablation, so that increases the series resistance of the contact region 12 and thus forms a series resistor for the OLED panel. By removing resistance material, for example by means of incisions in the resistance layer, the cross section of the resistance material is changed, ie reduced, or its effective length is increased using a focused laser beam. This increases the electrical resistance. This procedure is applicable to perform a resistance increase. With regard to the sectional shape, it is possible, for example, to make straight cuts from the side transversely to the resistance path. With high matching accuracies, one can use a so-called L-cut, which consists of a transverse incision and an adjoining, running along the resistance path section. The latter longitudinal cut causes a smaller change in resistance per cut length and therefore allows a finer resistance balance. In Fig. La, only a transverse incision for extending the resistance path and thus to increase the desired resistance value is shown.

According to a further exemplary embodiment of the present invention, as illustrated in FIG. 2 a-b, a plurality of contact regions in the divided electrodes can also be provided with a tunable resistance element for coupling out the operating current at which a resistance compensation can be carried out. For this reason, in each case the required resistance value at the contact areas of the contact area provided for contacting can be determined both for the contact areas 12 (eg anode contact areas) provided for contacting the first electrode layer 11a and for the contact areas 13 (eg cathode contact areas) provided for contacting the second electrode layer 11c OLED panels are determined to obtain the most homogeneous luminance distribution of the OLED panel. The determination of the respective resistance values for the contact regions of the OLED panel provided for contacting can then be carried out in accordance with the procedure of measuring inhomogeneities for each contact region of the OLED panel provided for contacting in accordance with the first exemplary embodiment. Also in this case, each contact region 12, 13, whose resistance value is to be designed to be adjustable, has a tunable resistance element 12a, 13a. In the context of all exemplary embodiments of the present invention, it should be noted that according to the phrase "a contact region, a tunable resistance element can be patterned or adjusted to, for example, at least a region of the contact region itself in order to change the resistance at the contact region make. Further, additional tunable resistance structures may be disposed on or electrically connected to the respective contact areas 12, 13 to provide a tunable resistance element at the respective contact areas.

If, according to the further exemplary embodiment of the present invention, the resistance values required for a more homogeneous luminance distribution of the OLED panel are determined both at the contact regions 12, 13 provided for contacting the first electrode layer 11a and at the contact regions 12c for contacting the second electrode layer 11c, As shown in Fig. 2b, the resistance values at both connection types, ie the anode terminals and the cathode terminals are changed. FIG. 2b again shows an enlarged detail view of the corner area of the OLED panel 10 with the active layer stack 11 and the contact areas 12, 13. As shown in FIG. 2b, sections 15 and 16 are provided in the connection contacts, these sections can be provided by removing resistance material in the form of cuts or depressions in the resistive layer of the respective contact area with a focused laser beam, so that the cross-section of the resistive element decreases, whereby the resulting electrical resistance can be selectively increased.

The cross-sections shown in Fig. 2b are again assumed only by way of example, and also in the embodiments shown in Fig. 2b equally longitudinal sections can be provided to increase the resistance value instead of the cross-sections. Here, too, any suitable process for the targeted removal of material of the resistance element can be used to set the resistance value.

According to the exemplary embodiment illustrated with reference to FIGS. 2a-b, the series resistance of the OLED panel can be changed in order to reduce the effects of interfering contact and contact resistances on the homogeneity of the luminance distribution over the emission surface of the planar luminous body, wherein the resistance compensation also corresponds to the procedure can be performed in the first embodiment. FIG. 3 now shows a schematic plan view of an OLED panel 10, the OLED panel 10 having an active layer stack 11 and contact regions 12, 13 for contacting the active layer stack 11. In this case, for example, the contact region 12 as the anode contact region and the contact region 13 as the cathode contact region (or um- swept) be formed. The contact regions 12, 13 can now optionally each have a tunable resistance element 12a, 13a (corresponding to the embodiments shown above). As is now shown in FIG. 3, a contact region 12 (eg anode contact region) provided for example for contacting the first electrode layer 11a and the contact region 13 (eg cathode contact region) provided for contacting the second electrode layer 11c is now with respect to the internal resistance of the contact region 12 OLED panels high resistance element 40 is provided, which is thus connected between the contact areas 12 and 13. The resistance element 40 can now again be made adjustable. In this exemplary embodiment too, the tunable resistance element 40 can each have a tunable thick-film resistor structure, a trimmable thin-film resistor structure, a trimmable SMD resistor element or a trimmable integrated resistor structure, which in turn can be applied to the respective one by means of a laser trimming operation or a laser ablation process required resistance value can be set or increased.

Alternatively, as the tunable resistive element 40, an adjustable potentiometer or a programmable electronic load circuit may be used, in which case the respective resistance value of the potentiometer or the programmable electronic load circuit may be adjusted to the respective required resistance value. Alternatively, as the tunable resistive element 40, a solid resistive element, e.g. an SMD resistance element having a fixed resistance value which corresponds to the respective required resistance value for achieving a homogeneous luminance distribution, is connected between the contact areas 12, 13 in order to achieve the respectively required resistance values for a more homogeneous luminance distribution by a parallel connection of the contact areas 12, 13 of the OLED Panels 10 provide.

According to the exemplary embodiment illustrated in FIG. 3, a trimmable resistor is provided parallel to the light-emitting layer 12 at the contact regions 12, 13, that is to say between the contact region 12 provided for contacting the first electrode layer 11a and that for contacting the second electrode layer 11c provided contact area 13 a relatively high resistance 40 is provided. If a plurality of contact regions 12 are provided for current injection and a plurality of contact regions 13 for current decoupling, it is also possible to arrange a plurality of adjustable resistance elements 40 between respectively assigned contact regions 12, 13. Thus, a calibratable resistance element 40 parallel to the light-emitting layer 11, that is to say in parallel, can also be provided at a plurality of contact regions 12, 13 the input and output terminal, the OLED panel 10 are switched. This additional, parallel-connected adjustable resistance element 40 is to be selected to be relatively high-impedance, for example in a range from 500 ohms or one kilo-ohms (ie, for example in a range of 0.5 to 50 kilo-ohms), so that only a relatively small current flow flows through this parallel-connected adjustable resistor element 40 and thus the power loss is kept low by this resistor element 40. Further, the resistance of the tunable resistor element 40 may be selected to be more than 10 or 20 times the internal resistance of the OLED panel. By providing this further, adjustable resistance element 40 parallel to the active, light-emitting layer stack 11, a further adjustment parameter or degree of freedom is obtained, which can be varied in order to counteract possible inhomogeneities in the luminance of the OLED panel 10.

With the additional tunable resistance element 40, not only asymmetries at the lead resistances can be compensated, but also local inhomogeneities within the electrode layer materials (cathode or anode layer) and the organic, light-emitting layer (s) can be reduced or compensated. Based on the parallel to the active layer stack 11 additionally arranged tunable resistance element 40, for example, the diode characteristic of the OLED panel can be adjusted to a certain extent. Based on the additional resistance element 40 between the contact regions 12, 13, a parallel resistance element can thus be formed to the diode-effective OLED panel 10, while a variable resistor or resistor can be provided by the adjustable resistor elements 12a, 13b provided at the contact regions 12 (and optionally 13) ., Serial resistance to the diode-effective OLED panel 10 can be formed.

Thus, according to the invention, an increase in the homogeneity of the luminance distribution over the emission surface of the OLED panel can be achieved either via the targeted adjustment of the series resistance (series resistance) or the parallel resistance or via a suitable combination of the series and parallel resistance.

The embodiment shown in FIG. 4a shows in side view an OLED module in which an OLED panel 10 is connected to a base element 20, for example a circuit board. The OLED module has defined electrical (and possibly other) interfaces, so that such an OLED module can be installed in a simple manner without an individual adaptation in a luminaire. One function of such an OLED module would then be, inter alia, the flow of defined interfaces (external contacts) to the respective contacting station optimized to the shape of the OLED panel. len / contact areas of the OLED panel to distribute. The OLED module thus has intermediate contact areas 26, 27 on a first main surface of the board 20 facing the OLED panel 10, which are electrically connected to the contact areas provided on the OLED panel for contacting the OLED panel. The circuit board 20 further has external contacts 21, 22 on a second main surface, the external contacts 21, 22 of the board 20 being electrically connected by the board 20 to the intermediate contact areas 26, 27 on the first main surface. The external contacts 21, 22 are provided, for example, to be electrically connected to a support plate (not shown), for example a lamp (or a socket) and the contacts there.

With regard to the circuit board 20, it is pointed out that it can have, for example, two (or even a larger number) of external contacts at predefined, standardized contacting points, which then extend from the second main surface of the board 20 to, for example, four or more intermediate contact areas on the board first main surface of the board 20 may be performed. Thus, the operating current for the planar luminous body of, for example, two external contacts within the board 20 can be performed on a larger number of intermediate contacts on the first main surface of the board 20 to the OLED contact areas, i. the contact areas 12, 13 of the OLED panel 10, to contact. This contacting between the intermediate contact areas on the board 20 to the contact areas 12, 13 on the OLED panel is indicated schematically in FIG. 4 a by the electrically conductive connecting elements 32, 33.

In Fig. 4a, an OLED panel 10 is connected to a circuit board 20 to form the OLED module. According to the invention, however, it is equally possible to arrange a plurality of OLED panels 10 on the board 20 in each case in order to form an OLED module with a plurality of OLED panels 10, which in turn can be fastened to the carrier board or inserted into a socket , The OLED panel 10 can be fastened to the circuit board 20 by means of any desired mechanical fastening elements (for example by means of adhesive or solder material). In FIG. 4 a, the OLED panel is mechanically connected to the circuit board 20 by means of an adhesive layer 36.

After the determination of the resistance value or the resistance values required for a more homogeneous luminance distribution of the OLED panel 10 based on the detected position, expansion and / or luminance of one or more inhomogeneities in the luminance distribution, it is now possible, for example, to adjust to the resistance value required for a more homogeneous luminance distribution or the resistance values at the contact areas of the circuit board 20 at tunable resistance belts provided there. 21a, 22a. Thus, for example, a tunable resistance element 21a, 22a is connected in series between the intermediate contact 26, 27 on the first main surface of the circuit board 20, which is connected to the at least one contact region 12 of the OLED panel 10, and the associated external contact 21, 22. Thus, according to the invention, for example, between each outer contact 21, 22 of the board 20 and each associated intermediate contact 26, 27 of the board 20, a tunable resistance element 21a, 22a are switched, the corresponding to the respective determined resistance value for the associated contact area on the OLED panel 10 on the required resistance value can be adjusted.

Also in this embodiment, the tunable resistive element 21a, 22a disposed on the board 20 may each comprise a tunable thick film resistive structure, a trimmable thin film resistor structure, a trimmable SMD resistive element or a trimmable integrated resistor structure, again by means of a laser trimming operation or a laser ablation process can be set or increased to the respective required resistance value.

Alternatively, an adjustable potentiometer or a programmable electronic load circuit can be used as respective tunable resistance element 21a, 22a, in which case the respective resistance value of the potentiometer or of the programmable electronic load circuit can be set to the respective required resistance value.

Alternatively, using a circuit board 20, a solid resistive element, e.g. an SMD resistance element having a fixed resistance value corresponding to the respective required resistance value for achieving a symmetrical contacting, in each case connected in series between the external contact 21, 22 of the circuit board 20 and the associated intermediate contact of the circuit board, by the resistance value respectively required for a more homogeneous luminance distribution to provide at the contact areas 12, 13 of the OLED panel 10.

With regard to the previously described setting of the resistance value required for a homogenous luminance distribution at one or more contact regions 12, 13 of the OLED panel 10 or between a contact region 12 provided for impressing current and a contact region 13 of the OLED panel 10 for increasing the current the homogeneity of the luminance of a flat luminous element is further indicated that the respective resistance compensation, ie the adjustment to the required resistance value, before or even after the It is possible for the OLED panel to be encapsulated since the required setting of the resistance values can be carried out on externally accessible areas of the OLED panel or OLED module. With regard to the embodiments illustrated above, it is pointed out that the trimmable thick-film resistor structures or trimmable thin-film resistor structures designed as tunable resistance elements can also be arranged as conductor tracks on the OLED panel 10 or the circuit board 20. In the context of the present invention, it is further pointed out that when determining the respective resistance value required for a more homogeneous luminance distribution of the OLED panel at at least one of the plurality of contacting areas of the OLED panel, this resistance value is within a tolerance range with respect to the exact an absolutely homogeneous luminance distribution of the contact areas is determined, the resistance value being determined, for example, with a minimum accuracy of more than 50%, 80% or 95% with respect to the exact resistance value (for an absolutely homogeneous luminance distribution).

Likewise, it should be noted that when the respective resistance value is set on the at least one of the plurality of contact regions provided on the resistance value required for a homogeneous luminance distribution of the OLED panel, this resistance value setting is again within a tolerance range with an accuracy of more than 50%, 80 % or 95% can be done on the respective determined resistance value. The tolerance ranges in the setting of the resistance value can result, for example, from the tolerances in the adjustment of the resistance values by means of a laser trimming process or a laser ablation process.

In the method according to the invention for increasing the homogeneity of the luminance distribution over the emission surface of a flat luminous body, which has an OLED panel with a plurality of contact regions 12 for feeding in an operating current and at least one contact region 13 for decoupling the operating current, then one for a homogeneous luminance distribution of the OLED panel 10 required resistance value at least one of the plurality of contact areas provided for contacting 12, 13 determined. The resistance value at the at least one of the plurality of contact regions 12, 13 provided for contacting is then set to the resistance value required for a more homogeneous luminance distribution of the OLED panel 10. With regard to the above description, it is pointed out that the exemplary exemplary embodiments illustrated with reference to FIGS. 1a-b, 2a-b, and 3 refer to an OLED or an OLED panel 10, while that described with reference to FIGS. 4a-b illustrated embodiment relates to an OLED module. According to the invention, both an OLED panel and an OLED module can be subsumed under the generic term "flat luminous body".

The concept of the invention for improving the homogeneity of the luminance homogeneity achieved by a flat luminous element (OLED panel or OLED module) is therefore equally applicable to an OLED panel and. an OLED module applicable.

The exemplary embodiments described above with reference to FIGS. 1a-b, 2a-b, 3 and 4b each show a plan view of an OLED panel with the contact regions 12, 13. With respect to the contact region 12, 13, it should be noted that these are used for Contacting the various electrode layers I Ia, 11c of the layer stack 11 may be located in different planes to each other, wherein the contact areas 12, 13 are spatially and electrically separated from each other, for example by means of insulating spacer structures. The invention is not limited by the description based on embodiments. Rather, the invention includes any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if the feature or combination itself is not explicitly mentioned in the claims or exemplary embodiments.

Claims

claims

Flat luminous element with the following features:

a layer arrangement (10) having a first electrode layer (I la), a second electrode layer (11c) and at least one light emitting layer (1 lb) therebetween, wherein a plurality of contact regions (12) for contacting the first electrode layer (I Ia) and at least one contact region (13) is provided for contacting the second electrode layer (11c), at least one contact region (12, 13) of the contact regions (12, 13) provided for contacting having a tunable resistance element (12a, 13a, 21a, 22a), or wherein a tunable resistance element (40) is connected between a contact region (12) provided for contacting the first electrode layer and a contact region (13) provided for contacting the second electrode layer, the resistance value of the tunable resistance element (12a, 13a; 21a, 22a; 40) is adjustable to a changed resistance value.

A planar illuminant according to claim 1, wherein the resistance value of the tunable resistive element (12a, 13a; 21a, 22a; 40) is adjustable by means of a laser trimming operation or a laser ablation process.

A planar luminous element according to claim 1 or 2, wherein the layer arrangement (10) is connected to a base element (20), in particular a printed circuit board, and the base element (20) has intermediate contact regions (26, 27) on one of the first layer arrangement (10). facing main surface, which are connected to the contact areas (12, 13) of the layer assembly (10), and external contacts (21, 22) on a second main surface, with the associated intermediate contact areas (26, 27) on the first main surface of the base member (20) are electrically connected, wherein the tunable resistance element (21a, 22a) is connected in series between the intermediate contact region (26, 27) on the first main surface of the base element (20) and the at least one contact region ( 12, 13) of the layer arrangement (10) is electrically connected, and the associated external contact (21, 22) is connected or wherein a non-compensatable resistance element (21a, 22a) with the resistance value required for a more homogeneous luminance distribution is connected in series between the intermediate contact region (26, 27) on the first main surface of the base element (20) which is connected to the at least one contact region (12 , 13) of the layer arrangement (10) is connected, and the associated external contact (21, 22) is connected.

4. The planar luminous element according to claim 1, wherein the tunable resistance element has a trimmable thick-film resistor structure, a trimmable thin-film resistor structure, a trimmable SMD resistor element or a trimmable integrated resistor structure.

5. Flat luminous element according to one of the preceding claims, wherein the tunable resistance element comprises an adjustable potentiometer or a programmable electronic load circuit.

6. Flat luminous element according to one of the preceding claims, wherein the layer arrangement (10) has a plurality of contact regions (13) for contacting the second electrode layer (11c).

7. A planar luminous element according to one of the preceding claims, wherein each of the contacting areas provided for the contact areas (12, 13) comprises a tunable resistance element.

8. The planar luminous element according to one of the preceding claims, wherein the first electrode layer (I Ia) is formed as an anode layer of the layer arrangement (10) and the second electrode layer (11c) as a cathode layer of the layer arrangement (10).

9. The planar luminous element according to claim 1, wherein the first electrode layer is formed as a cathode layer of the layer arrangement and the second electrode layer is formed as an anode layer of the layer arrangement.

10. A method for increasing the homogeneity of the luminance of a flat luminous body, wherein the flat luminous body has a layer arrangement (10) with a first An electrode layer, a second electrode layer and at least one intermediate light-emitting layer and a plurality of contact regions for contacting the first electrode layer and at least one contact region for contacting the second electrode layer, comprising the following steps:

Determining a resistance value required for a more homogeneous luminance distribution of the layer arrangement on at least one of the plurality for contacting the contact areas (12, 13) of the layer arrangement (10), which results in a more homogeneous luminance distribution of the layer arrangement (10) than an unchanged resistance value; and

Setting the resistance value at the at least one of the plurality of contact areas provided for contacting (12, 13) on the required for a more homogeneous luminance distribution of the layer assembly (10) resistance value.

11. The method of claim 10, wherein the step of determining comprises the substep of:

Evaluating the homogeneity of the luminance distribution achieved by the layer arrangement (10) in the case of an operating current feed, wherein the resistance value required for a more homogeneous luminance density distribution can be determined on the basis of the luminance distribution.

12. The method of claim 11, wherein the step of evaluating comprises the following substeps:

Detecting a position, extent and / or luminance of an inhomogeneity in the luminance distribution, and

Determining the required for a more homogeneous luminance distribution resistance value based on the detected position, extent and / or luminance.

13. The method according to any one of claims 10 to 12, wherein the at least one contact region (12, 13) comprises a tunable resistance element (12a, 13a), wherein the step of adjusting the resistance value by means of a Resistance adjustment to the tunable resistance element (12a, 13a) is performed.

14. The method according to any one of claims 10 to 13, wherein between one of the provided for contacting the first electrode layer contact areas (12) and provided for contacting the second electrode layer contact area (13) a tunable resistance element (40) is connected, wherein the Step of adjusting the resistance value by means of a resistance compensation is performed on the tunable resistance element (40).

15. The method of claim 13 or 14, wherein the resistance compensation is performed by means of a laser trimming operation or a laser ablation process.

16. The method according to any one of claims 10 to 15, wherein the layer assembly (10) is connected to a base member 20, in particular a circuit board, and the base member (20) intermediate contact areas on one of the first, the layer assembly (10) facing the main surface with the contact areas (12, 13) of the layer arrangement (10) are electrically connected, and external contacts (21, 22) on a second main surface, which are electrically connected to the associated Zwischenkontaktb ereichen on the first main surface of the base member (20), wherein in the step of adjusting the resistance value, a resistance compensation is performed on a tunable resistance element (21a, 22a) connected in series between the intermediate contact area on the first main surface of the base element (20) and the at least one contact area (12, 13). the layer assembly (10) is connected, and the associated external contact (21, 22) is connected, or wob in the step of setting the resistance value, a non-compensatable resistance element (21a, 22a) having the resistance value determined for a more homogeneous luminance distribution serially between the contact region on the first main surface of the base element (20) and the at least one contact region (12 , 13) of the layer arrangement (10), and to the associated th outer contact (21, 22) is arranged.

17. The method of claim 13, wherein the tunable resistive element comprises a trimmable thick film resistor structure, a trimmable thin film resistor structure, a trimmable SMD resistor element, or a trimmable integrated resistor structure, wherein the step of adjusting the resistance value is by a laser trimming operation or a laser ablation process is carried out.

18. The method of claim 13, wherein the tunable resistive element comprises an adjustable potentiometer or a programmable electronic load circuit, wherein in the step of adjusting the resistance value, the resistance of the potentiometer or the programmable electronic load circuit is adjusted.

19. The method of claim 10, wherein the layer arrangement further has a plurality of contact regions for contacting the second electrode layer.

A method according to any one of claims 10 to 19, wherein each of the contacting portions (12, 13) comprises a tunable resistance element (12a, 13a), the steps of determining and setting a resistance value for each of the plurality of contacts Contact areas (12, 13) is performed.